Scientific Intelligence—Mineralogy. 365 
SCIENTIFIC INTELLIGENCE. 
MINERALOGY. 
1. Sir David Brewster on the origin of the Diamond.—Sir 
David ascribes the origin of the diamond to a slow decomposition of 
plants. He met with a diamond which contained a globule of air, 
while the surrounding substance of the diamond had a polarizing 
(doubly refracting) structure, displayed by four sectors of polarized 
light encircling the globule. He therefore inferred that this air- 
bubble had been heated, and, by expansion, had produced pressure 
on the surrounding parts of the diamond, and thereby communicated 
to them a polarizing structure. Now, for this to have happened, 
the diamond must have been soft and susceptible of compression. 
But as various circumstances contribute to prove that this softness 
was the effect of neither solvents nor heat, he concluded that the 
diamond must have been formed, like amber, by the consolidation 
of vegetable matter, which gradually acquired a crystalline form by 
the influence of time and slow action of corpuscular forces.—(Pe- 
reira’s Lectures on Polarized Light.) 
2. Polarity of Crystals——TIn crystals, it is necessary to admit, 
besides ordinary attraction and repulsion, a third molecular force, 
called polarity, which may be regarded either as an original or a 
“derivative property. Without this, it is impossible to account for 
the regularity of crystalline forms. Under the influence of a mu- 
tually attractive force, particles would adhere together and form 
masses, the shapes of which, however, would be subject to the 
greatest variety ; and though, occasionally, they might happen to 
be regular, yet this could not constantly be the case. 
The simplest conception we can form of polarity is, that it de- 
pends on the unequal action of molecular attraction or repulsion in 
different directions. A molecule endowed with unequal attractive 
forces in different directions, may be said to be possessed of polarity. 
—(Dr Pereira’s Lectures on Polarized Light.) 
3. Researches on Crystallization.—M. Lavalle has recently pre- 
sented to the French Academy a memoir narrating some remark- 
able phenomena discovered and patiently observed by him. All 
bodies, whose composition is clearly defined, have a tendency to 
crystallize; in other words, when they take the solid state slowly, 
their last particles, in grouping themselves, each after the other, are 
so disposed as to form a mass, which the mind successively decom- 
poses into plane layers, into rectilinear files, and into elementary 
particles. As these are disposed parallel to each other, and at 
equal distances, to be arranged in files, so the layers are formed by 
the assembly of parallel and equidistant files; so, also, parallelism 
